Version:  2.0.40 2.2.26 2.4.37 3.5 3.6 3.7 3.8 3.9 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 4.0 4.1

Linux/mm/mremap.c

  1 /*
  2  *      mm/mremap.c
  3  *
  4  *      (C) Copyright 1996 Linus Torvalds
  5  *
  6  *      Address space accounting code   <alan@lxorguk.ukuu.org.uk>
  7  *      (C) Copyright 2002 Red Hat Inc, All Rights Reserved
  8  */
  9 
 10 #include <linux/mm.h>
 11 #include <linux/hugetlb.h>
 12 #include <linux/shm.h>
 13 #include <linux/ksm.h>
 14 #include <linux/mman.h>
 15 #include <linux/swap.h>
 16 #include <linux/capability.h>
 17 #include <linux/fs.h>
 18 #include <linux/swapops.h>
 19 #include <linux/highmem.h>
 20 #include <linux/security.h>
 21 #include <linux/syscalls.h>
 22 #include <linux/mmu_notifier.h>
 23 #include <linux/sched/sysctl.h>
 24 #include <linux/uaccess.h>
 25 
 26 #include <asm/cacheflush.h>
 27 #include <asm/tlbflush.h>
 28 
 29 #include "internal.h"
 30 
 31 static pmd_t *get_old_pmd(struct mm_struct *mm, unsigned long addr)
 32 {
 33         pgd_t *pgd;
 34         pud_t *pud;
 35         pmd_t *pmd;
 36 
 37         pgd = pgd_offset(mm, addr);
 38         if (pgd_none_or_clear_bad(pgd))
 39                 return NULL;
 40 
 41         pud = pud_offset(pgd, addr);
 42         if (pud_none_or_clear_bad(pud))
 43                 return NULL;
 44 
 45         pmd = pmd_offset(pud, addr);
 46         if (pmd_none(*pmd))
 47                 return NULL;
 48 
 49         return pmd;
 50 }
 51 
 52 static pmd_t *alloc_new_pmd(struct mm_struct *mm, struct vm_area_struct *vma,
 53                             unsigned long addr)
 54 {
 55         pgd_t *pgd;
 56         pud_t *pud;
 57         pmd_t *pmd;
 58 
 59         pgd = pgd_offset(mm, addr);
 60         pud = pud_alloc(mm, pgd, addr);
 61         if (!pud)
 62                 return NULL;
 63 
 64         pmd = pmd_alloc(mm, pud, addr);
 65         if (!pmd)
 66                 return NULL;
 67 
 68         VM_BUG_ON(pmd_trans_huge(*pmd));
 69 
 70         return pmd;
 71 }
 72 
 73 static pte_t move_soft_dirty_pte(pte_t pte)
 74 {
 75         /*
 76          * Set soft dirty bit so we can notice
 77          * in userspace the ptes were moved.
 78          */
 79 #ifdef CONFIG_MEM_SOFT_DIRTY
 80         if (pte_present(pte))
 81                 pte = pte_mksoft_dirty(pte);
 82         else if (is_swap_pte(pte))
 83                 pte = pte_swp_mksoft_dirty(pte);
 84 #endif
 85         return pte;
 86 }
 87 
 88 static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
 89                 unsigned long old_addr, unsigned long old_end,
 90                 struct vm_area_struct *new_vma, pmd_t *new_pmd,
 91                 unsigned long new_addr, bool need_rmap_locks)
 92 {
 93         struct address_space *mapping = NULL;
 94         struct anon_vma *anon_vma = NULL;
 95         struct mm_struct *mm = vma->vm_mm;
 96         pte_t *old_pte, *new_pte, pte;
 97         spinlock_t *old_ptl, *new_ptl;
 98 
 99         /*
100          * When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
101          * locks to ensure that rmap will always observe either the old or the
102          * new ptes. This is the easiest way to avoid races with
103          * truncate_pagecache(), page migration, etc...
104          *
105          * When need_rmap_locks is false, we use other ways to avoid
106          * such races:
107          *
108          * - During exec() shift_arg_pages(), we use a specially tagged vma
109          *   which rmap call sites look for using is_vma_temporary_stack().
110          *
111          * - During mremap(), new_vma is often known to be placed after vma
112          *   in rmap traversal order. This ensures rmap will always observe
113          *   either the old pte, or the new pte, or both (the page table locks
114          *   serialize access to individual ptes, but only rmap traversal
115          *   order guarantees that we won't miss both the old and new ptes).
116          */
117         if (need_rmap_locks) {
118                 if (vma->vm_file) {
119                         mapping = vma->vm_file->f_mapping;
120                         i_mmap_lock_write(mapping);
121                 }
122                 if (vma->anon_vma) {
123                         anon_vma = vma->anon_vma;
124                         anon_vma_lock_write(anon_vma);
125                 }
126         }
127 
128         /*
129          * We don't have to worry about the ordering of src and dst
130          * pte locks because exclusive mmap_sem prevents deadlock.
131          */
132         old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
133         new_pte = pte_offset_map(new_pmd, new_addr);
134         new_ptl = pte_lockptr(mm, new_pmd);
135         if (new_ptl != old_ptl)
136                 spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
137         arch_enter_lazy_mmu_mode();
138 
139         for (; old_addr < old_end; old_pte++, old_addr += PAGE_SIZE,
140                                    new_pte++, new_addr += PAGE_SIZE) {
141                 if (pte_none(*old_pte))
142                         continue;
143                 pte = ptep_get_and_clear(mm, old_addr, old_pte);
144                 pte = move_pte(pte, new_vma->vm_page_prot, old_addr, new_addr);
145                 pte = move_soft_dirty_pte(pte);
146                 set_pte_at(mm, new_addr, new_pte, pte);
147         }
148 
149         arch_leave_lazy_mmu_mode();
150         if (new_ptl != old_ptl)
151                 spin_unlock(new_ptl);
152         pte_unmap(new_pte - 1);
153         pte_unmap_unlock(old_pte - 1, old_ptl);
154         if (anon_vma)
155                 anon_vma_unlock_write(anon_vma);
156         if (mapping)
157                 i_mmap_unlock_write(mapping);
158 }
159 
160 #define LATENCY_LIMIT   (64 * PAGE_SIZE)
161 
162 unsigned long move_page_tables(struct vm_area_struct *vma,
163                 unsigned long old_addr, struct vm_area_struct *new_vma,
164                 unsigned long new_addr, unsigned long len,
165                 bool need_rmap_locks)
166 {
167         unsigned long extent, next, old_end;
168         pmd_t *old_pmd, *new_pmd;
169         bool need_flush = false;
170         unsigned long mmun_start;       /* For mmu_notifiers */
171         unsigned long mmun_end;         /* For mmu_notifiers */
172 
173         old_end = old_addr + len;
174         flush_cache_range(vma, old_addr, old_end);
175 
176         mmun_start = old_addr;
177         mmun_end   = old_end;
178         mmu_notifier_invalidate_range_start(vma->vm_mm, mmun_start, mmun_end);
179 
180         for (; old_addr < old_end; old_addr += extent, new_addr += extent) {
181                 cond_resched();
182                 next = (old_addr + PMD_SIZE) & PMD_MASK;
183                 /* even if next overflowed, extent below will be ok */
184                 extent = next - old_addr;
185                 if (extent > old_end - old_addr)
186                         extent = old_end - old_addr;
187                 old_pmd = get_old_pmd(vma->vm_mm, old_addr);
188                 if (!old_pmd)
189                         continue;
190                 new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
191                 if (!new_pmd)
192                         break;
193                 if (pmd_trans_huge(*old_pmd)) {
194                         int err = 0;
195                         if (extent == HPAGE_PMD_SIZE) {
196                                 VM_BUG_ON_VMA(vma->vm_file || !vma->anon_vma,
197                                               vma);
198                                 /* See comment in move_ptes() */
199                                 if (need_rmap_locks)
200                                         anon_vma_lock_write(vma->anon_vma);
201                                 err = move_huge_pmd(vma, new_vma, old_addr,
202                                                     new_addr, old_end,
203                                                     old_pmd, new_pmd);
204                                 if (need_rmap_locks)
205                                         anon_vma_unlock_write(vma->anon_vma);
206                         }
207                         if (err > 0) {
208                                 need_flush = true;
209                                 continue;
210                         } else if (!err) {
211                                 split_huge_page_pmd(vma, old_addr, old_pmd);
212                         }
213                         VM_BUG_ON(pmd_trans_huge(*old_pmd));
214                 }
215                 if (pmd_none(*new_pmd) && __pte_alloc(new_vma->vm_mm, new_vma,
216                                                       new_pmd, new_addr))
217                         break;
218                 next = (new_addr + PMD_SIZE) & PMD_MASK;
219                 if (extent > next - new_addr)
220                         extent = next - new_addr;
221                 if (extent > LATENCY_LIMIT)
222                         extent = LATENCY_LIMIT;
223                 move_ptes(vma, old_pmd, old_addr, old_addr + extent,
224                           new_vma, new_pmd, new_addr, need_rmap_locks);
225                 need_flush = true;
226         }
227         if (likely(need_flush))
228                 flush_tlb_range(vma, old_end-len, old_addr);
229 
230         mmu_notifier_invalidate_range_end(vma->vm_mm, mmun_start, mmun_end);
231 
232         return len + old_addr - old_end;        /* how much done */
233 }
234 
235 static unsigned long move_vma(struct vm_area_struct *vma,
236                 unsigned long old_addr, unsigned long old_len,
237                 unsigned long new_len, unsigned long new_addr, bool *locked)
238 {
239         struct mm_struct *mm = vma->vm_mm;
240         struct vm_area_struct *new_vma;
241         unsigned long vm_flags = vma->vm_flags;
242         unsigned long new_pgoff;
243         unsigned long moved_len;
244         unsigned long excess = 0;
245         unsigned long hiwater_vm;
246         int split = 0;
247         int err;
248         bool need_rmap_locks;
249 
250         /*
251          * We'd prefer to avoid failure later on in do_munmap:
252          * which may split one vma into three before unmapping.
253          */
254         if (mm->map_count >= sysctl_max_map_count - 3)
255                 return -ENOMEM;
256 
257         /*
258          * Advise KSM to break any KSM pages in the area to be moved:
259          * it would be confusing if they were to turn up at the new
260          * location, where they happen to coincide with different KSM
261          * pages recently unmapped.  But leave vma->vm_flags as it was,
262          * so KSM can come around to merge on vma and new_vma afterwards.
263          */
264         err = ksm_madvise(vma, old_addr, old_addr + old_len,
265                                                 MADV_UNMERGEABLE, &vm_flags);
266         if (err)
267                 return err;
268 
269         new_pgoff = vma->vm_pgoff + ((old_addr - vma->vm_start) >> PAGE_SHIFT);
270         new_vma = copy_vma(&vma, new_addr, new_len, new_pgoff,
271                            &need_rmap_locks);
272         if (!new_vma)
273                 return -ENOMEM;
274 
275         moved_len = move_page_tables(vma, old_addr, new_vma, new_addr, old_len,
276                                      need_rmap_locks);
277         if (moved_len < old_len) {
278                 /*
279                  * On error, move entries back from new area to old,
280                  * which will succeed since page tables still there,
281                  * and then proceed to unmap new area instead of old.
282                  */
283                 move_page_tables(new_vma, new_addr, vma, old_addr, moved_len,
284                                  true);
285                 vma = new_vma;
286                 old_len = new_len;
287                 old_addr = new_addr;
288                 new_addr = -ENOMEM;
289         } else if (vma->vm_file && vma->vm_file->f_op->mremap) {
290                 err = vma->vm_file->f_op->mremap(vma->vm_file, new_vma);
291                 if (err < 0) {
292                         move_page_tables(new_vma, new_addr, vma, old_addr,
293                                          moved_len, true);
294                         return err;
295                 }
296         }
297 
298         /* Conceal VM_ACCOUNT so old reservation is not undone */
299         if (vm_flags & VM_ACCOUNT) {
300                 vma->vm_flags &= ~VM_ACCOUNT;
301                 excess = vma->vm_end - vma->vm_start - old_len;
302                 if (old_addr > vma->vm_start &&
303                     old_addr + old_len < vma->vm_end)
304                         split = 1;
305         }
306 
307         /*
308          * If we failed to move page tables we still do total_vm increment
309          * since do_munmap() will decrement it by old_len == new_len.
310          *
311          * Since total_vm is about to be raised artificially high for a
312          * moment, we need to restore high watermark afterwards: if stats
313          * are taken meanwhile, total_vm and hiwater_vm appear too high.
314          * If this were a serious issue, we'd add a flag to do_munmap().
315          */
316         hiwater_vm = mm->hiwater_vm;
317         vm_stat_account(mm, vma->vm_flags, vma->vm_file, new_len>>PAGE_SHIFT);
318 
319         if (do_munmap(mm, old_addr, old_len) < 0) {
320                 /* OOM: unable to split vma, just get accounts right */
321                 vm_unacct_memory(excess >> PAGE_SHIFT);
322                 excess = 0;
323         }
324         mm->hiwater_vm = hiwater_vm;
325 
326         /* Restore VM_ACCOUNT if one or two pieces of vma left */
327         if (excess) {
328                 vma->vm_flags |= VM_ACCOUNT;
329                 if (split)
330                         vma->vm_next->vm_flags |= VM_ACCOUNT;
331         }
332 
333         if (vm_flags & VM_LOCKED) {
334                 mm->locked_vm += new_len >> PAGE_SHIFT;
335                 *locked = true;
336         }
337 
338         return new_addr;
339 }
340 
341 static struct vm_area_struct *vma_to_resize(unsigned long addr,
342         unsigned long old_len, unsigned long new_len, unsigned long *p)
343 {
344         struct mm_struct *mm = current->mm;
345         struct vm_area_struct *vma = find_vma(mm, addr);
346 
347         if (!vma || vma->vm_start > addr)
348                 return ERR_PTR(-EFAULT);
349 
350         if (is_vm_hugetlb_page(vma))
351                 return ERR_PTR(-EINVAL);
352 
353         /* We can't remap across vm area boundaries */
354         if (old_len > vma->vm_end - addr)
355                 return ERR_PTR(-EFAULT);
356 
357         /* Need to be careful about a growing mapping */
358         if (new_len > old_len) {
359                 unsigned long pgoff;
360 
361                 if (vma->vm_flags & (VM_DONTEXPAND | VM_PFNMAP))
362                         return ERR_PTR(-EFAULT);
363                 pgoff = (addr - vma->vm_start) >> PAGE_SHIFT;
364                 pgoff += vma->vm_pgoff;
365                 if (pgoff + (new_len >> PAGE_SHIFT) < pgoff)
366                         return ERR_PTR(-EINVAL);
367         }
368 
369         if (vma->vm_flags & VM_LOCKED) {
370                 unsigned long locked, lock_limit;
371                 locked = mm->locked_vm << PAGE_SHIFT;
372                 lock_limit = rlimit(RLIMIT_MEMLOCK);
373                 locked += new_len - old_len;
374                 if (locked > lock_limit && !capable(CAP_IPC_LOCK))
375                         return ERR_PTR(-EAGAIN);
376         }
377 
378         if (!may_expand_vm(mm, (new_len - old_len) >> PAGE_SHIFT))
379                 return ERR_PTR(-ENOMEM);
380 
381         if (vma->vm_flags & VM_ACCOUNT) {
382                 unsigned long charged = (new_len - old_len) >> PAGE_SHIFT;
383                 if (security_vm_enough_memory_mm(mm, charged))
384                         return ERR_PTR(-ENOMEM);
385                 *p = charged;
386         }
387 
388         return vma;
389 }
390 
391 static unsigned long mremap_to(unsigned long addr, unsigned long old_len,
392                 unsigned long new_addr, unsigned long new_len, bool *locked)
393 {
394         struct mm_struct *mm = current->mm;
395         struct vm_area_struct *vma;
396         unsigned long ret = -EINVAL;
397         unsigned long charged = 0;
398         unsigned long map_flags;
399 
400         if (new_addr & ~PAGE_MASK)
401                 goto out;
402 
403         if (new_len > TASK_SIZE || new_addr > TASK_SIZE - new_len)
404                 goto out;
405 
406         /* Check if the location we're moving into overlaps the
407          * old location at all, and fail if it does.
408          */
409         if ((new_addr <= addr) && (new_addr+new_len) > addr)
410                 goto out;
411 
412         if ((addr <= new_addr) && (addr+old_len) > new_addr)
413                 goto out;
414 
415         ret = do_munmap(mm, new_addr, new_len);
416         if (ret)
417                 goto out;
418 
419         if (old_len >= new_len) {
420                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
421                 if (ret && old_len != new_len)
422                         goto out;
423                 old_len = new_len;
424         }
425 
426         vma = vma_to_resize(addr, old_len, new_len, &charged);
427         if (IS_ERR(vma)) {
428                 ret = PTR_ERR(vma);
429                 goto out;
430         }
431 
432         map_flags = MAP_FIXED;
433         if (vma->vm_flags & VM_MAYSHARE)
434                 map_flags |= MAP_SHARED;
435 
436         ret = get_unmapped_area(vma->vm_file, new_addr, new_len, vma->vm_pgoff +
437                                 ((addr - vma->vm_start) >> PAGE_SHIFT),
438                                 map_flags);
439         if (ret & ~PAGE_MASK)
440                 goto out1;
441 
442         ret = move_vma(vma, addr, old_len, new_len, new_addr, locked);
443         if (!(ret & ~PAGE_MASK))
444                 goto out;
445 out1:
446         vm_unacct_memory(charged);
447 
448 out:
449         return ret;
450 }
451 
452 static int vma_expandable(struct vm_area_struct *vma, unsigned long delta)
453 {
454         unsigned long end = vma->vm_end + delta;
455         if (end < vma->vm_end) /* overflow */
456                 return 0;
457         if (vma->vm_next && vma->vm_next->vm_start < end) /* intersection */
458                 return 0;
459         if (get_unmapped_area(NULL, vma->vm_start, end - vma->vm_start,
460                               0, MAP_FIXED) & ~PAGE_MASK)
461                 return 0;
462         return 1;
463 }
464 
465 /*
466  * Expand (or shrink) an existing mapping, potentially moving it at the
467  * same time (controlled by the MREMAP_MAYMOVE flag and available VM space)
468  *
469  * MREMAP_FIXED option added 5-Dec-1999 by Benjamin LaHaise
470  * This option implies MREMAP_MAYMOVE.
471  */
472 SYSCALL_DEFINE5(mremap, unsigned long, addr, unsigned long, old_len,
473                 unsigned long, new_len, unsigned long, flags,
474                 unsigned long, new_addr)
475 {
476         struct mm_struct *mm = current->mm;
477         struct vm_area_struct *vma;
478         unsigned long ret = -EINVAL;
479         unsigned long charged = 0;
480         bool locked = false;
481 
482         if (flags & ~(MREMAP_FIXED | MREMAP_MAYMOVE))
483                 return ret;
484 
485         if (flags & MREMAP_FIXED && !(flags & MREMAP_MAYMOVE))
486                 return ret;
487 
488         if (addr & ~PAGE_MASK)
489                 return ret;
490 
491         old_len = PAGE_ALIGN(old_len);
492         new_len = PAGE_ALIGN(new_len);
493 
494         /*
495          * We allow a zero old-len as a special case
496          * for DOS-emu "duplicate shm area" thing. But
497          * a zero new-len is nonsensical.
498          */
499         if (!new_len)
500                 return ret;
501 
502         down_write(&current->mm->mmap_sem);
503 
504         if (flags & MREMAP_FIXED) {
505                 ret = mremap_to(addr, old_len, new_addr, new_len,
506                                 &locked);
507                 goto out;
508         }
509 
510         /*
511          * Always allow a shrinking remap: that just unmaps
512          * the unnecessary pages..
513          * do_munmap does all the needed commit accounting
514          */
515         if (old_len >= new_len) {
516                 ret = do_munmap(mm, addr+new_len, old_len - new_len);
517                 if (ret && old_len != new_len)
518                         goto out;
519                 ret = addr;
520                 goto out;
521         }
522 
523         /*
524          * Ok, we need to grow..
525          */
526         vma = vma_to_resize(addr, old_len, new_len, &charged);
527         if (IS_ERR(vma)) {
528                 ret = PTR_ERR(vma);
529                 goto out;
530         }
531 
532         /* old_len exactly to the end of the area..
533          */
534         if (old_len == vma->vm_end - addr) {
535                 /* can we just expand the current mapping? */
536                 if (vma_expandable(vma, new_len - old_len)) {
537                         int pages = (new_len - old_len) >> PAGE_SHIFT;
538 
539                         if (vma_adjust(vma, vma->vm_start, addr + new_len,
540                                        vma->vm_pgoff, NULL)) {
541                                 ret = -ENOMEM;
542                                 goto out;
543                         }
544 
545                         vm_stat_account(mm, vma->vm_flags, vma->vm_file, pages);
546                         if (vma->vm_flags & VM_LOCKED) {
547                                 mm->locked_vm += pages;
548                                 locked = true;
549                                 new_addr = addr;
550                         }
551                         ret = addr;
552                         goto out;
553                 }
554         }
555 
556         /*
557          * We weren't able to just expand or shrink the area,
558          * we need to create a new one and move it..
559          */
560         ret = -ENOMEM;
561         if (flags & MREMAP_MAYMOVE) {
562                 unsigned long map_flags = 0;
563                 if (vma->vm_flags & VM_MAYSHARE)
564                         map_flags |= MAP_SHARED;
565 
566                 new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
567                                         vma->vm_pgoff +
568                                         ((addr - vma->vm_start) >> PAGE_SHIFT),
569                                         map_flags);
570                 if (new_addr & ~PAGE_MASK) {
571                         ret = new_addr;
572                         goto out;
573                 }
574 
575                 ret = move_vma(vma, addr, old_len, new_len, new_addr, &locked);
576         }
577 out:
578         if (ret & ~PAGE_MASK)
579                 vm_unacct_memory(charged);
580         up_write(&current->mm->mmap_sem);
581         if (locked && new_len > old_len)
582                 mm_populate(new_addr + old_len, new_len - old_len);
583         return ret;
584 }
585 

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